Biodiesel and bioethanol are the main biofuels that are currently available for commercial use. These biofuels can be easily manufactured from renewable feedstock (e.g. biomass) with existing technology. However, many applications that use standard fuels cannot easily be converted to use biodiesel or bioethanol. There are differences in the physical and chemical properties of biodiesel and bioethanol compared to standard fuels, such as differences in energy density, flammability, boiling point range (or lack thereof), shelf life and solvent properties. The specification of the fuel that may be used with many engines is very specific and may not permit the use of existing biofuel alternatives, such as biodiesel and bioethanol. There is therefore a need for new, alternative biofuels and processes for producing the biofuels economically on an industrial scale.
Electrolysis is known in the art as a method for performing chemical reactions on a laboratory scale. Laboratory experiments where a normal Kolbe-reaction is prevented by drastically changed reaction conditions have been performed for more than 100 years, beginning with Moest et. al. (German patent 138442, issued 1903) who created alcohols, aldehydes and ketones from fatty acids using electrolysis. His research was late honoured by naming this type of electrochemical decarboxylation after him (“Hofer-Moest reaction”) and it spawned numerous other interesting applications in the chemical literature, none of which, however, has achieved any degree of commercial significance.
A comprehensive overview of the scientific background of this invention can be found in “Organic Electrochemistry” by Henning Lund, Manuel M. Baizer, Ole Hammerich, Chapters 12/14, ISBN: 0824704304 by CRC Press. Kronenthal et al focussed on aliphatic ethers, and on methoxy-undecane in particular (U.S. Pat. No. 2,760,926, issued in 1956), but achieved yields of 40% or less while consuming large amounts of electricity (by at least a factor ten judging from the voltage applied (90+ Volts). Use of these, or any other similar ethers, in a mix with hydrocarbons for fuels as suggested here, finds no mention in the literature.
More recently, however, in WO 2007/095215 and WO 2007/027669 the original Kolbe-reaction was quoted as a means, among numerous other techniques, to create useful hydrocarbons utilizing fatty acids of renewable origin. However due to the nature of the Kolbe-reaction, the chain length would almost double in the process, creating a mix of C30-C34 hydrocarbons that would need extensive conventional refining to yield useable, liquid transportation fuels. This may be contrasted with a one-step specialized Hofer-Moest process.
It would be possible to manufacture said liquid fuels by means of a regular, crossed Kolbe-electrolysis, e.g. using oleic acid and acetic acid as feedstock. This procedure would yield a C18-hydrocarbon and would maintain the desired cis-/“Z-” configuration of the double bond. However, it is believed that such a technique would be far less economical due to the consumption of acetic acid, the costly use of platinum anodes, and the low-value byproducts.(i.e. ethane and a doubly unsaturated C34 hydrocarbon in this case) generally unavoidable in a crossed Kolbe reaction.
It has been reported that oil companies cooperating with producers of animal fat and/or vegetable oil create hydrocarbons from triglycerides, making straight C16/C18 alkanes and propane (from the glycerol contained in fats/oils). However, this process uses a catalyst and totally hydrogenates feedstock at high pressures and temperatures. It consumes large amounts of hydrogen and destroys all special cis/“Z-” oriented double bonds. The process described in this application can preserve such double bonds and can generate hydrogen as a by-product.